Isocyanate-curing coating material and method for application thereof

Abstract

An isocyanate-curing coating material is disclosed which essentially consists of (A) an agent formed of a hydroxyl group-containing polymer having a weight average molecular weight in the range of 1000-20000 and (B) a polyisocyanate compound as a curing agent containing at least three isocyanate groups in the molecular unit thereof and having a weight average molecular weight in the range of 400-3000 and incorporating (A) the agent and (B) the curing agent in such amounts that the isocyanate groups in (B) the curing agent amounts to 0.5-2 equivalent weights per equivalent weight of the hydroxyl group in (A) the agent. A method for spray coating the isocyanate-curing coating material is also disclosed which comprises the steps of mixing (A) the agent with (B) the curing agent in a coating device, heating the resultant mixture therein to a temperature in the range of 35-80 DEG C., and spraying the hot mixture directly on a given object with the coating device.

What is claimed is: 
     
       1. An isocyanate-curing coating material, comprising (A) an agent formed of a hydroxyl group-containing polymer having a weight average molecular weight in the range of 1000-20000 and (B) a polyisocyanate compound as a curing, agent containing at least three isocyanate groups in the molecular unit thereof and having a weight average molecular weight in the range of 400-3000 and incorporating (A) said agent and (B) said curing agent in such amounts that said isocyanate groups in (B) said curing agent amounts to 0.5-2 equivalent weights per equivalent weight of the hydroxyl group in (A) said agent, wherein said hydroxyl group-containing polymer is at least one member selected from the group consisting of acryl polyols and polyester polyols,   wherein said acryl polyol consists essentially of acryl monomers possessed of a hydroxyl group, an acrylic acid monomer, and at least one other monomer selected from the group consisting of acryl monomers not possessed of a hydroxyl group, and vinyl monomers, and   wherein said acrylic acid monomer is present in an amount of about 1% by weight of said acryl polyol, and wherein said acryl monomers possessed of a hydroxyl group are present in an amount of about 15% by weight of said acryl polyol.   
     
     
       2. An isocyanate-curing coating material according to claim 1, wherein said acryl monomer possessed of a hydroxyl group is at least one member selected from the group consisting of 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxpropyl acrylate, 4-hydroxybutyl acrylate and lactone-modified α, β-ethylenically unsaturated monomers having 1-10 mols of a lactone added to (meth)acrylic hydroxyalkyl esters. 
     
     
       3. An isocyanate-curing coating material according to claim 1, wherein said acryl monomer not possessed of a hydroxyl group or said vinyl monomer is at least one member selected from the group consisting of methyl (meth)acrylate, n-butyl (meth)-acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, styrene, and α-methyl styrene. 
     
     
       4. An isocyanate-curing coating material according to claim 1, wherein said acryl polyol has a weight average molecular weight in the range of 3000-10000 and a hydroxyl group number in the range of 50-150. 
     
     
       5. An isocyanate-curing coating material according to claim 1, wherein said polyester polyol consists of at least one member selected from the group consisting of phthalic anhydride, isophthalic acid, glycerin, and trimethylol propane. 
     
     
       6. An isocyanate-curing coating material according to claim 1, wherein said polyester polyol has a weight average molecular weight in the range of 4000-10000 and a hydroxyl group number in the range of 50-150. 
     
     
       7. An isocyanate-curing coating material according to claim 1, wherein said polyisocyanate compound comprises at least one member selected from the group consisting of hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), hydrated xylylene diisocyanate (H-XDI), xylylene diisocyanate (XDI), and meta-tetramethyl xylylene diisocyanate (TMXDI). 
     
     
       8. An isocyanate-curing coating material according to claim 1, wherein said polyisocyanate compound has a weight average molecular weight in the range of 500-1500. 
     
     
       9. The isocyanate-curing coating material according to claim 1, wherein the hydroxyl group-containing, polymer is an acryl polyol. 
     
     
       10. The isocyanate-curing coating material according, to claim 1, wherein the hydroxyl group-containing polymer is a polyester polyol. 
     
     
       11. A method of spray coating the isocyanate-curing coating material of claim 1 comprising the steps of mixing agent (A) with agent (B) in a coating device, heating the resultant mixture therein to a temperature in the range of 35-80° C. and spraying the hot mixture directly on an object with said coating device. 
     
     
       12. A method according to claim 1, wherein said acryl monomer possessed of a hydroxyl group is at least one member selected from the group consisting of such (meth)acrylic hydroxyalkyl esters as 2-hydroxyethyl methacrylate, 2-hydroxy-ethyl acrylate, hydroxypropyl methacrylate, hydroxy-propyl acrylate, and 4-hydroxybutyl acrylate and lactone-modified α, β-ethylenically unsaturated monomers having 1-10 mols of such a lactone as ε-caprolactone or γ-butyrolactone added to (meth)-acrylic hydroxyalkyl esters. 
     
     
       13. A method according to claim 1, wherein said acryl monomer not possessed of a hydroxyl group or said vinyl monomer is at least one member selected from the group consisting of methyl (meth)acrylate, n-butyl (meth)-acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, styrene, and α-methyl styrene. 
     
     
       14. A method according to claim 1, wherein said acryl polyol has a weight average molecular weight in the range of 3000-10000 and a hydroxyl group number in the range of 50-150. 
     
     
       15. A method according to claim 1, wherein said polyester polyol consists of at least one member selected from the group consisting of phthalic anhydride, isophthalic acid, glycerin, and trimethylol propane. 
     
     
       16. A method according to claim 1, wherein said polyester polyol has a weight average molecular weight in the range of 4000-10000 and a hydroxyl group number in the range of 50-150. 
     
     
       17. A method according to claim 1, wherein said polyisocyanate compound comprises at least one member selected from the group consisting of hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), hydrated xylylene diisocyanate (H-XDI), xylylene diisocyanate (XDI), and meta-tetramethyl xylylene diisocyanate (TMXDI). 
     
     
       18. A method according to claim 1, wherein said polyisocyanate compound has a weight average molecular weight in the range of 500-1500.